> -----Original Message----- > From: Peter Rosin [mailto:p...@axentia.se] > Sent: Saturday, December 17, 2016 10:29 PM > To: linux-kernel@vger.kernel.org > Cc: Peter Rosin <p...@axentia.se>; Vadim Pasternak > <vad...@mellanox.com>; Michael Shych <michae...@mellanox.com>; > Wolfram Sang <w...@the-dreams.de>; linux-...@vger.kernel.org > Subject: [PATCH] i2c: mux: mlxcpld: fix i2c mux selection caching > > smbus functions return -ve on error, 0 on success. However, > __i2c_transfer() have a different return signature - -ve on error, or number > of buffers transferred (which may be zero or greater.) > > The upshot of this is that the sense of the text is reversed when using the > mux on a bus supporting the master_xfer method: we cache the value and > never retry if we fail to transfer any buffers, but if we succeed, we clear > the > cached value > > Fix this by making mlxcpld_mux_reg_write() return a -ve error code for all > failure cases, just as was done in commit 7f638c1cb0a1 ("i2c: mux: > pca954x: fix i2c mux selection caching") > > This also aligns the implementations of these two muxes in this area. > > Signed-off-by: Peter Rosin <p...@axentia.se> > ---
Acked-by: Vadim Pasternak <vad...@mellanox.com> > > Hi! > > I audited the other i2c muxes for similar problems after the recent regression > report for the pca954x driver [1], and found only this. > > I obviously don't have the hardware to test this patch. > > Anyway, this driver is probably lower profile than the pca954x, but this still > needs fixing in my opinion... > > Cheers, > peda > > [1] http://www.spinics.net/lists/linux-i2c/msg27586.html > > drivers/i2c/muxes/i2c-mux-mlxcpld.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/drivers/i2c/muxes/i2c-mux-mlxcpld.c b/drivers/i2c/muxes/i2c- > mux-mlxcpld.c > index 3ab654bbfab5..b7ca249ec9c3 100644 > --- a/drivers/i2c/muxes/i2c-mux-mlxcpld.c > +++ b/drivers/i2c/muxes/i2c-mux-mlxcpld.c > @@ -95,6 +95,7 @@ static int mlxcpld_mux_reg_write(struct i2c_adapter > *adap, > struct i2c_client *client, u8 val) { > struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client- > >dev); > + int ret = -ENODEV; > > if (adap->algo->master_xfer) { > struct i2c_msg msg; > @@ -104,17 +105,21 @@ static int mlxcpld_mux_reg_write(struct > i2c_adapter *adap, > msg.flags = 0; > msg.len = 2; > msg.buf = msgbuf; > - return __i2c_transfer(adap, &msg, 1); > + ret = __i2c_transfer(adap, &msg, 1); > + > + if (ret >= 0 && ret != 1) > + ret = -EREMOTEIO; > } else if (adap->algo->smbus_xfer) { > union i2c_smbus_data data; > > data.byte = val; > - return adap->algo->smbus_xfer(adap, client->addr, > - client->flags, I2C_SMBUS_WRITE, > - pdata->sel_reg_addr, > - I2C_SMBUS_BYTE_DATA, &data); > - } else > - return -ENODEV; > + ret = adap->algo->smbus_xfer(adap, client->addr, > + client->flags, I2C_SMBUS_WRITE, > + pdata->sel_reg_addr, > + I2C_SMBUS_BYTE_DATA, &data); > + } > + > + return ret; > } > > static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan) > @@ -127,10 +132,7 @@ static int mlxcpld_mux_select_chan(struct > i2c_mux_core *muxc, u32 chan) > /* Only select the channel if its different from the last channel */ > if (data->last_chan != regval) { > err = mlxcpld_mux_reg_write(muxc->parent, client, regval); > - if (err) > - data->last_chan = 0; > - else > - data->last_chan = regval; > + data->last_chan = err < 0 ? 0 : regval; > } > > return err; > -- > 2.1.4
